Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$92.37	11.716%	$103.1921	$103.19	$103.20	$103.20
Purchase #2	$86.43	5.180%	$90.9071	$90.91	$90.90	$90.90
Purchase #3	$92.86	11.352%	$103.4015	$103.40	$103.40	$103.40
Purchase #4	$6.27	11.762%	$7.0075	$7.01	$7.00	$7.00
Purchase #5	$194.98	6.354%	$207.369	$207.37	$207.35	$207.40
Purchase #6	$113.73	11.305%	$126.5872	$126.59	$126.60	$126.60
Purchase #7	$155.92	7.171%	$167.101	$167.10	$167.10	$167.10
7 purchase totals =	$742.56		$805.5654	$805.57	$805.55	$805.60